Tactical rifle

ABSTRACT

A tactical combat rifle includes a two-part, bolt carrier. The upper part of the bolt carrier rides on rails formed in an upper receiver while the lower part of the bolt carrier, although attached to the upper part and moving with it, engages no supporting surfaces. A piston, driven by combustion gases from a regulatable gas block assembly, strikes the upper bolt carrier in the center of its mass to propel it rearward. The barrel is threaded to a removable barrel extension and secured to the upper receiver. A non-reciprocating charging handle is located far forward and accessible from either side of the upper receiver so the user does not have to lower the rifle from the shoulder or take eyes off the target. Combustion debris is kept away from the lower receiver and bolt so operation is cleaner and cycling rates of fire steadier.

TECHNOLOGICAL FIELD

The technological field of the disclosed tactical combat rifle is thefield of small arms. More particularly, the technological field isrifles configured for use in a variety of combat situations.

BACKGROUND

Rifles have been the dominate small arm in combat for at least 200years. In that time, they have evolved to be more accurate, lighter, andable to fire ammunition farther and at a higher rate.

Rifles have also evolved as a weapons platform from the time they werefirst designed to carry a bayonet. Present day rifles may carryadditional equipment, such as sighting devices, laser markers, andadditional weapons such as grenade launchers.

Rifles can operate quieter by using suppressors, may be less visible byusing flash hiders, and more comfortable because of reduced weight,improved adjustability, and buffered butt stocks.

The capabilities of rifles as a weapons platform may overshadow howsophisticated they are from a purely mechanical point of view, that is,how their various parts cooperate together in the blink of an eye to usethe pressure wave from firing a round of ammunition for rapidly andprecisely reloading the rifle.

Yet there is room for improvement. Rifles may be used for differentpurposes in combat, such as perimeter defense, close quarterengagements, sniping, and assaulting an enemy force. Rifles are oftenused in physically hostile places, where they will come in contact withcold or hot weather, dirt, sand, mud, and vegetation. Rifles may now beexpected to fire more rounds over their useful life and in all types ofweather and environmental conditions. All of these factors challengedesigners of tactical combat rifles to produce a safer, more reliable,more flexible and more durable rifle.

SUMMARY

The present tactical rifle includes a large, two-part, bolt carrier. Theupper part of the bolt carrier rides on rails formed in the insides ofan upper receiver, while the lower part of the bolt carrier is suspendedfrom the upper part, and does not ride on its own supporting surfaces.The upper and lower parts of the bolt carrier move together smoothly andas one unit.

The bolt carrier is propelled rearward by a piston that is drivenrearward by the pressure of combustion gases released on firing a roundof ammunition. The piston strikes the bolt carrier in its center of massfor efficient and smooth action. Using a field-adjustable regulator,combustion gas available to the gas block assembly for movement of thebolt carrier may be adjusted by the user to vent a portion of thecombustion gas to the atmosphere if a suppressor is attached to thebarrel or to vent less gas when the rifle is being used in dustyconditions. The ability of the user to regulate gas pressure allows thecycling rate to be maintained despite changing operationalcircumstances.

The barrel of the present rifle is held to the receiver by a barrelextension. Two screws and a recoil lug hold the barrel extensionsecurely in place. Removal of the two screws enables the user to replacethe barrel or select a different barrel. If desired, the user can selecta different barrel, different caliber ammunition, and the correspondingbolt for that ammunition.

The bolt area is kept cleaner by the present design. For example, thebolt is not unlocked from the chamber after a round has been fired untilthe pressure in the chamber has declined to near ambient pressureconditions so that little combustion particulate will be blown from thechamber when it is opened onto the end of the bolt and into the lowerreceiver. Furthermore, the gas block is positioned well forward of andabove the bolt so debris from the gas block is also kept away from thebolt and lower receiver.

The rifle has a non-reciprocating charging handle, mounted fartherforward on the upper receiver on either side of the upper receiver so asto be operable by both left- and right-handed shooters, and sufficientlyfar forward so that the shooter can continue to sight a target, therifle continuing to remain on the shooter's shoulder while the usercharges the gun.

These and other features and their advantages will be apparent to thoseskilled in the art of tactical rifle design from a careful reading theDetailed Description accompanied by the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures,

FIG. 1 shows a right side, exterior view of the present tactical rifle,according to an aspect of the disclosure;

FIG. 2 shows a right side, cross-sectional view of the tactical rifle ofFIG. 1 with the bolt closed, according to an aspect of the disclosure;

FIGS. 3A and 3B are smaller scale views of the right side,cross-sectional view of the tactical rifle of FIG. 2, with FIG. 3Ashowing the rear portion of the rifle of FIG. 2 and with FIG. 3B showingthe forward portion of the rifle of FIG. 2, according to an aspect ofthe disclosure;

FIGS. 4A and 4B show right side, cross-sectional views of the rifle ofFIGS. 3A and 3B, respectively, with the bolt carrier fully recoiledafter firing a round of ammunition, according to an aspect of thedisclosure;

FIG. 5 shows a right side, cross-sectional view of the forward end ofthe rifle of FIG. 3B with the charging handle pulled rearward, accordingto an aspect of the disclosure;

FIGS. 6A and 6B show right side, cross-sectional views of rifle of FIGS.2A and 2B, respectively, with the bolt just released from the chamberafter firing the rifle, according to an aspect of the disclosure;

FIG. 7 is a cross-sectional of the upper receiver showing the rails fromwhich the bolt carrier and charging sled are supported, according toaspects of the disclosure;

FIG. 8 is a perspective view of charging sled, according to an aspect ofthe disclosure;

FIG. 9 is a side view of the catch, according to an aspect of thedisclosure;

FIGS. 10A and 10B are left front perspective and left sidecross-sectional views of an attachment for a gas block to the barrel,according to an aspect of the disclosure;

FIGS. 11A, 11B, and 11C show a left rear perspective view, a left sidecross-sectional view, and rear end, partial cross-sectional view of agas regulator, according to aspects of the disclosure.

FIGS. 12A, 12B, 12C, and 12D show a left front perspective view, a frontcross-sectional view, a left side exterior view, a left sidecross-sectional view of lower bolt carrier, respectively, according toaspects of the disclosure;

FIG. 13 is a rearward, right side view of bolt without the extractor,according to an aspect of the disclosure;

FIGS. 14A and 14B show a side exterior view of an extractor and aperspective view of extractor threaded pivot pin, according to an aspectof the disclosure;

FIG. 15 is a right side exterior view of the cam pin of the bolt,according to an aspect of the present disclosure;

FIGS. 16A, 16B, 16C, and 16D show a rear right perspective view, a rearview, and a right side cross-sectional view of the barrel extension, anda perspective view of the recoil lug, according to aspects of thedisclosure; and

FIGS. 17A and 17B show perspective and side views of the limit pin,according to aspects of the disclosure.

DETAILED DESCRIPTION

Herein is disclosed a rifle, referred to as a tactical combat riflebecause of its capability to be altered for different uses in a combatenvironment. It is a combat rifle, primarily, being designed forfighting an enemy under difficult conditions and to fire a large numberof rounds of ammunition dependably and in semi-automatic or fullyautomatic mode over an extended lifetime as a firearm.

FIG. 1 shows the present rifle, generally referred to by referencenumber 10, from the right side according to the perspective of a shooterholding the rifle in a right-handed firing position. A right-handedshooter tucks a buttstock 14 of rifle 10 into his or her shoulder,places the fingers of a right hand around a pistol grip 18, which ispart of a lower receiver assembly 22, and an index finger on trigger 26inside trigger guard 30 just behind a magazine 34 that is inserted in amagazine well 38. The right-handed shooter would extend his or her leftarm forward along the left side of rifle 10 to support its distal end,the distal end being the end opposing the proximal end that is nearer toshooter, and would point the distal end of a barrel 42 at a target.

A significant difference in rifle 10 that is readily noticeable from theexterior is a long upper receiver 46. Upper receiver 46 encloses much ofbarrel 42 and may be made of a light-weight but sturdy material, such asaluminum. An aluminum upper receiver 46 may be extruded and thenmachined to complete the details of its construction.

FIG. 2 shows rifle 10 in a cross-sectional side view. In thatcross-sectional view, the details of the interior structure include,from the left or proximal end of rifle 10, a bumper 50, an operatinggroup spring 54, an operating rod 58, and a buffer 62. Buffer 62receives the recoil of a bolt carrier 66 following the firing of a roundof ammunition. Bolt carrier 66 is driven rapidly rearward, that is, tothe left or proximal end of rifle 10 as shown in FIG. 2, therebycompressing operating spring 54. Operating spring 54 is then relieved asthe force on buffer 62 dissipates. The recoil of bolt carrier 66 isabsorbed largely by the resiliency of spring 54 and bumper 50 ratherthan by the shooter.

Forward of buffer 62 is lower receiver assembly 22 which includes apistol grip 18, a trigger 26, a trigger guard 30, a magazine well 38,and a sear 68. A magazine 34 is shown in magazine well 38.

Upper receiver 46 is also shown in a transverse cross-sectional view inFIG. 7, which shows the interior 44 of upper receiver, including firstrails 78 and second rails 104. Bolt carrier 66 is supported by secondrails 104. As will be described further below, barrel 42 is supported byfirst rails 78.

Bolt carrier 66 includes both an upper bolt carrier 70 and a lower boltcarrier 74. Upper bolt carrier 70 and lower bolt carrier 74 are attachedfirmly together, such as by brazing at their interface at 72, seen inFIG. 4A, so they move together throughout the firing cycle. Upper boltcarrier 70 rides on second rails 104 in upper receiver 46. The weight oflower bolt carrier 74 is completely supported by upper bolt carrier 70on second set of rails 104. Although lower bolt carrier 74 carries abolt 82, a firing pin 86, and a cam pin 182 (best seen in FIG. 16),upper bolt carrier 70, being very long, provides the support required tocarry lower bolt carrier 74 through its firing cycle.

FIGS. 3A and 3B show a smaller scale version of FIG. 2, dividing rifle10 into separate rearward (FIG. 3A) and forward (FIG. 3B) portions. Atthe forward end of upper receiver 46 is a charging handle 94. Charginghandle 94 may be operated using the shooter's preferred hand from theexterior of rifle 10. FIG. 3B shows rifle 10 having a charging handle 94that is accessible from the left side for a right-handed shooter.Interior to receiver 46, but visible through a long slot 48 formed inreceiver 46 (the right side of rifle 10 being symmetric to the left sidewith respect to charging operations) is a charging sled 98, which isshown in perspective from the right rear in FIG. 8. Charging sled 98 hasopposing downward depending legs 100 that ride on second rails 104toward the top of upper the interior 44 of receiver 46, as best seen inFIG. 7.

Charging sled 98 temporarily connects charging handle 94 to upper boltcarrier 70. As seen in FIG. 5, pivoting catch 102 (shown in detail inFIG. 9) on charging sled 98 is biased downward by a spring about pivotpin 106 but hooks the top of bolt carrier 70 when bolt carrier 70 is outof battery and then is pivoted upward again by camming pin 110 torelease bolt carrier 70 when charging handle 94 is returned to itsforward position, shown in FIG. 3B. Compare also FIG. 4B, in whichcharging handle 94 is in its rearward most position, and FIG. 6B, inwhich charging handle 94 is nearly in its forward-most position.Otherwise, charging handle 94 moves independently of upper receiver 46and only pivots catch 102 when the user moves charging handle 94rearward.

Upper bolt carrier 70 and lower bolt carrier 74 move rearward as a unitand far enough when rifle 10 is being charged so that bolt 82 ejects aspent shell casing through an ejection port 190 (see FIG. 1) on theright side of rifle 10. Then, as the operator moves charging handle 94forward or releases charging handle 94, thereby allowing operatingspring 54 to move bolt 82 forward, bolt 82 pushes a new round out ofmagazine 34 and into chamber 80 of barrel 42.

Once returned to its forward position, catch 102 is forced to pivotclockwise on engagement with a camming pin 110 which forces the distalend of catch 102 clockwise. Camming pin 110 thus prevents charging sled98 and charging handle 94 from reciprocating with bolt carrier 66 duringthe firing cycle.

The forward location of charging handle 94 enables the operator of rifle10 to maintain focus on a target while reaching forward with a supporthand to operate it. Use of charging handle 94 obviates the need to takerifle 10 off the user's shoulder or the user's eye off a target. Theuser can maintain the target in sight while reaching forward with hissupport hand to grasp charging handle 94 on whichever side of rifle hehas changing handle 94 installed, with charging handle 94 easily withinthe peripheral vision of the shooter when the shooter elects to chargerifle 10. Charging handle 94 also serves as a forward assist to pushammunition into chamber 80.

Except for movement of bolt carrier 66 using charging handle 94, boltcarrier 66 is otherwise moved by a gas block assembly located in thedistal end of upper receiver 46 where it is positioned at a distancefrom lower receiver 22 and lower bolt carrier 74, so that these criticalcomponents are less likely to be subject to the combustion gas anddebris from the barrel. See FIGS. 3B, 4B, 5, 10A, 10B, 11A, 11B, 11C,12A, 12B and 12C. The gas block assembly includes a piston 114 (seeFIGS. 3B, 4B, and 5), a barrel attachment 122 (FIGS. 10A and 10B), and aregulator (FIGS. 11A, 11B, and 11C).

Barrel attachment 122 surrounds and is secured to barrel 42. Barrelattachment 122 enables the interior of gas block 118 to communicate withthe interior of barrel 42 through a passage 134 in barrel attachment 122and a hole 146 in barrel 42 (best seen in FIGS. 3B, 4B, 5 and 6B). Whenpassage 134 and hole 146 are in registration, a portion of thecombustion gases that have been released by the firing of a round ofammunition pass from the interior of barrel 42 to the interior of gasblock 118 where they are available to provide the back pressure requiredfor moving piston 114 and thus bolt carrier 66 rearward againstoperating group spring 54.

FIG. 10A shows a perspective view of barrel attachment 122 from the leftfront, and FIG. 10B shows a left side, cross-sectional view of barrelattachment 122. Barrel attachment 122 has a lower portion 142 and anupper portion 150. Barrel 42 has a step 138 in its diameter at itsdistal end just posterior of the location of hole 146 (see FIG. 3B).Lower portion 142 of barrel attachment 122 has an interior 144dimensioned to receive barrel 42 just proximal of step 138 so that hole146 in barrel 42 may be aligned and be placed in registration withpassage 134 from lower portion 142 into upper portion 150 of barrelattachment 122. Upper portion 150 receives gas block 118 (best seen inFIGS. 11A, 11B, and 11C) into an interior 154 of upper portion 150 ofbarrel attachment 122 and, accordingly, the interior of barrel 42 isthen in fluid communication with channel 154. Gas block 118 is thussecured indirectly to barrel 42 by barrel attachment 122 and upperportion 150 of barrel attachment 122 and gas block 118 define channel154. A portion of combustion gases traveling down barrel 42 toward itsdistal end are thus received in channel 154 via hole 46 in barrel 42 andpassage 134 in barrel attachment 122 and are then used to provide theback pressure for operating bolt carrier 66.

The upper part 150 of barrel attachment 122 and gas block 118 arereceived in upper receiver 46. Piston 114 fits into upper part 150 ofbarrel attachment 122 but extends rearwardly outside barrel attachment122 in line with upper bolt carrier 70. The axial range of motion ofpiston 114 relative to barrel attachment 122 is limited, as can best beseen by comparing the position of piston 114 in channel 154 in FIG. 3B,before firing, and in channel 154 in FIG. 4B, after firing, which showthat an annular collar 152 on piston engages the narrowed end of channel154 of barrel attachment 122 on the rearward end of its travel which isa channel 156 of gas block 118 (FIG. 11A). Accordingly, when a round ofammunition is fired, combustion gases pass down barrel 42 and throughhole 146 of barrel 42, through passage 134 of barrel attachment 122, andinto channel 154 where, on the build-up of sufficient pressure forwardof labyrinth seals 116, the gas pressure impels piston 114 rearward inchannel 154 so its distal end strikes upper bolt carrier 70, thusdriving bolt carrier 70 rearward with sufficient force for it and lowerbolt carrier 74 to perform their cycling function.

Referring now to FIGS. 11A-11C but particularly FIG. 11B, which showsregulator 130 in cross section, the distal end of channel 154 of barrelattachment 122 communicates with a channel 156 in regulator 130 which isthreadedly received in barrel attachment 122. Channel 156 has two vents,namely, vent 170 and vent 174. Regulator 130 allows adjustments to bemade by the user in the amount of combustion gas used to drive piston114 by regulating the amount of combustion gas vented through eithervent 170 or vent 174 or not vented at all. The adjustments are made bymanually altering the rotational, or azimuthal, position of regulator130 with respect to barrel attachment 122 so that combustion gas canflow out smaller vent 170, larger vent 174, or not flow from any vent.When no gas is vented, there is more back pressure to drive piston 114rearward; when more gas is vented, less back pressure is available. Byselecting the right choice of vent or no vent, the cycling rate of rifle10 may be maintained within design range.

The first selection is the intermediate vent 170 for normal cyclingoperation, whereas vent 174 is selected for use with a suppressor onrifle 10. A suppressor attached to barrel 42 increases back pressure inbarrel 42 and thereby increases the cycling rate of fire. Therefore,larger hole 174 is selected to offset that greater backpressure causedby a suppressor and thereby provide a more normal back pressure level tomaintain the firing rate. The use of no hole may be reserved forcircumstances when additional back pressure may be needed to overcomeresistance to the movement of bolt carrier 66, such as when rifle 10 isin use in a dusty or dirty environment.

The choice of no vent, vent 170 and 174 is made by rotating regulator130 to select the appropriate position. The hexagonal sides of regulator130 may be marked to indicate which level of venting has been selected.The marking may include “Suppressed,” “Unsuppressed,” and “Adverse” (orabbreviations of these) for the choice of vent 174, 170, and no venting,respectively.

Referring now to FIGS. 12A-12D, lower bolt carrier 74 is shown. Lowerbolt carrier 74 carries bolt 82 and firing pin 86, which are best seenin FIG. 3A; and bolt 82 is best seen in FIG. 13. FIG. 12A shows aperspective view of lower bolt carrier 74. FIG. 12B is a cross-sectionalview of lower bolt carrier 74 to show a transverse hole 164 for a limitpin 168. Limit pin 168 is shown in perspective in FIG. 17A and in a sideview in FIG. 17B, while transverse hole 164 is also seen in FIGS.12A-12D but is also shown in relation to firing pin 86 in FIGS. 3A and4A. Limit pin 168 has a thinner portion 126 that engages annular flanges90 on firing pin 86 that limit axial movement of firing pin 86 withinlower bolt carrier 74. FIG. 12C is a side view of lower bolt carrier 74showing the shape of a cam path 178, which is on the side of lower boltcarrier 74.

Bolt 82, as shown in FIG. 13, includes a transversely mounted cam pin182, which is shown in FIG. 14. Cam pin 182 is a cylindrical pin with aflattened extension 172 that passes through a transverse hole 176 (seeFIGS. 3A, 4A, 6A) in bolt 82 thereby extending through cam path 178 inlower bolt carrier 74. Cam pin 182 also has a transverse hole 180through which firing pin 86 passes so that, as lower bolt carrier 74reciprocates, bolt 82 can rotate about the major axis of bolt carrier74, guided by the movement of flattened extension 172 in cam path 178.As lower bolt carrier 74 moves through upper receiver 46, cam pin 182rides on second rails 78 which forces bolt 82 to rotate through an anglewhen bolt carrier 74 moves to its forward-most position and flattenedextension 172 moves through cam path 178. The rotation of bolt 82 in therearward direction unlocks bolt 82 from chamber 80 and extracts a spentshell casing from chamber 80. The rotation of bolt 82 when moving in theforward direction selects the next round from magazine 34 and inserts itinto chamber 80.

The shape of cam path 178, and in particular, the vertical portion ofcam path 178, is such that it provides increased dwell time therebyproviding more time for chamber 80 pressure to drop closer toatmospheric pressure before bolt 82 is unlocked from chamber 80 and thuslimits blow back of combustion gases and debris into lower receiver 22and thereby prolongs the useful life of rifle 10.

Lugs 210 on the forward end of bolt 82 will line up with cutout portions214 formed in the entrance to barrel extension 198 so that bolt 82 cantravel freely in and out of barrel extension 198. Rotation of bolt 82will lock bolt 82 in barrel extension 198 and is caused when cam pin 182rides from one end of cam path 178 of lower bolt carrier 74 to theother, thereby, rotating bolt 82 first one way and then the oppositeway, to lock and unlock bolt 82 in barrel extension 198. A flat head 218on cam pin 182 rides in a channel form in the left side of upperreceiver 46 to rotate bolt 82 as cam pin 182 moves through a small angleto line up lugs 210 with cutout portions 214 of barrel extension 198.Upon clearing cutout portions 214, lugs 210 rotate further to lock bolt82 in barrel extension and seat a cartridge in chamber 80. At that pointin the cycle, bolt 82 is in its locked position.

Bolt 82 includes an extractor 186, shown in FIG. 14A, which is pivotallyattached to bolt 82 by a threaded screw 184, as best seen in FIG. 14B.Screw 184 is driven through a hole 188 in extractor when extractor 186is positioned between a pair of opposing holes 192 in bolt 82, as bestseen in FIG. 13. Threads on screw 184 help to hold extractor 186 to bolt82. Extractor 186 is designed to be robust, with a large radius 196 tobe better able to extract a large number of spent shell casings overtime. Shell casings are ejected to the right side of rifle 10 through anejection port 190 (see FIG. 1) past a deflector 194 that limits rearwardejection. Deflector 194 may be a molded part attached by a screw 196

Barrel 42 is held to upper receiver 46 by barrel extension 198. FIG. 16Ais a perspective view of barrel extension 198 from the right rear; FIG.10B is an end view of barrel extension 198; and FIG. 16C is across-sectional view of barrel extension 198, with barrel 42, as viewedfrom the left side of rifle 10. FIG. 16D is a recoil lug 220.

Barrel extension 198 has flanges 200, two on either side of it, thatrest on grooves 78 (See FIG. 7) of upper receiver 46 for support. Recoillug 220, in FIG. 16D and also in FIG. 16C, is similar to a washer but isan accurately ground and controlled structure that slides over thethreaded, proximal portion of barrel 42 and mates against a shoulder 226on barrel 42. Barrel extension 198 clamps recoil lug 220 onto barrel 42.Barrel extension 198, recoil lug 220, and barrel 42 all slide rearwardin upper receiver 46 and recoil lug 220 seats against a shoulder 226formed in barrel 42 (seen in FIG. 16C), which is its stopping point.Barrel extension 198 threads onto the proximal end of barrel 42 until itseats against recoil lug 220. Two screws 202 (see FIG. 2) threaded intoholes 204 formed in barrel extension 198 secure it to barrel 42 and inplace with respect to receiver 46. Holes 204 for screws 202 are slightlyoffset so that, when screws 202 are driven into holes 204, screws 202tend to pull barrel 42 rearward against receiver 46.

An external cover 206 is secured to receiver 46 underneath and laterallyof barrel extension 198. Cover 206 is held in place with one screw 208.

Similarly, removal of screws 202 allows barrel 42 to be removed. Ashorter or longer barrel 42 may be substituted, as needed, by the user.If bolt 82 is also replaced, the caliber of ammunition may be changed aswell. Accordingly, at the field level, rifle 10 may be customized fordifferent operational purposes. For example, a shorter barrel 42 may bebetter suited for close quarter combat and a longer one for perimeterguard duty.

Especially for use in fully automatic mode, there is a horizontal blindpassage 216 in the upper bolt carrier 70. Passage 216 may be filled withtungsten powder and welded closed to provide a means to mitigate “boltbounce.” Bolt bounce occurs when bolt carrier 66 impacts barrelextension 198 in the firing cycle. Bolt carrier 66 will tend to bounceback and then is driven forward immediately by operating group spring54. The tungsten powder in passage 216, however, will impact the end ofdistal end of passage 216 to counter the bounce in mitigation of carrierbounce. Eliminating dead bolt carrier bounce is important, especially infull automatic operation, because the bounce can cause a “failure tofire” event—when lower bolt carrier 74 bounces rearward far enough thatfiring pin 86 is not able to strike the cartridge primer.

Rifle 10 is piston-driven from the distal end of rifle 10 so all debrisfrom combustion tends to remain away from the rear, where lower boltcarrier 74 and lower receiver assembly 22 are located. Piston 114 hitsbolt carrier 66 at its center of its mass for greater transfer ofmomentum. Upper bolt carrier 70 then rides on rails 78 of upper receiver46, directly in line with piston 114. That riding surface is longerbecause upper receiver 46 is longer, making the movement of upper boltcarrier 70 smoother and surer.

Thus, the arrangement of the present rifle 10 provides a smoother firingplatform. The added mass of bolt carrier 66, the adjustability of buttstock 14, along with the added length of stroke and half inch thick 40durometer polyurethane bumper 50 and the elimination of blow back fromchamber 80 when bolt 82 is unlocked further smoothes operation andmaintains a steadier cycling rate.

When introducing elements of the present disclosure or exemplary aspectsor embodiment(s) thereof, the articles “a,” “an,” “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising,” “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. Although this disclosure has been described with respect tospecific embodiments, the details of these embodiments are not to beconstrued as limitations.

What is claimed is:
 1. A rifle, comprising: a barrel having a distal endand a proximal end and a chamber formed in said proximal end and a boreformed from said chamber to said distal end of said barrel and a holeformed in said bore of said barrel, a gas block assembly attached tosaid barrel, said gas block assembly having an interior in communicationwith said hole in said bore of said barrel; a piston slidably carried bysaid gas block assembly, said piston movable between a proximal positionand a distal position so that gas from said barrel travels through saidhole in said barrel to said interior of said gas block assembly anddrives said piston from said distal position to said proximal position;an upper receiver having rails, said barrel being housed in said upperreceiver; an upper bolt carrier slidable on said rails of said upperreceiver and in operating connection with said piston of said gas blockassembly so that when said piston slides proximally and strikes saidupper bolt carrier, said upper bolt carrier slides proximally inresponse thereto; a lower bolt carrier supported by and slidable withsaid upper bolt carrier; a bolt carried by said lower bolt carrier; afiring pin carried by said bolt; a lower receiver attached to said upperreceiver and having a trigger, and a magazine well proximate to saidtrigger and dimensioned for receiving an ammunition magazine; and a buttstock attached to said lower receiver.
 2. The rifle as recited in claim1, further comprising a barrel extension attached to said proximal endof said barrel, said barrel extension holding said proximal end of saidbarrel to said receiver.
 3. The rifle as recited in claim 1, furthercomprising a regulator attached to said gas block having an adjustablevent with at least two positions, a first position wherein relativelymore back pressure is delivered to said piston and a second positionwherein relatively less back pressure is delivered to said piston. 4.The rifle as recited in claim 1, wherein said upper bolt carrier andsaid lower bolt carrier are fastened together.
 5. The rifle as recitedin claim 1, wherein said receiver has a charging handle operable fromeither side of said upper receiver.
 6. The rifle as recited in claim 1,wherein said bolt rotates as it moves from its distal position to itsproximal position and wherein said bolt rotates to unlock from saidchamber after said pressure in said chamber has decreased.
 7. A rifle,comprising: a barrel having a distal end and a proximal end and achamber formed in said proximal end and a bore formed from said chamberto said distal end of said barrel and a hole formed in said bore of saidbarrel, said proximal end of said barrel having a threaded exterior; abarrel extension having a threaded interior dimensioned for receivingsaid proximal end of said barrel, said barrel extension having plurallugs; a gas block assembly attached to said distal end of said barrel,said gas block assembly having an interior in communication with saidhole in said bore of said barrel; a piston slidably carried by said gasblock assembly, said piston movable between a proximal position and adistal position so that gas from said barrel travels through said holein said barrel to said interior of said gas block assembly and drivessaid piston from said distal position to said proximal position; anupper receiver having first rails and second rails, said barrel beinghoused in said upper receiver, said lugs of said barrel extension beingsupported on said second rails of said upper receiver; an upper boltcarrier slidable on said first rails of said upper receiver and inoperating connection with said piston of said gas block assembly so thatwhen said piston slides proximally on said first rails and strikes saidupper bolt carrier, said upper bolt carrier slides proximally inresponse thereto; a lower bolt carrier supported by and slidable withsaid upper bolt carrier; a bolt carried by said lower bolt carrier; afiring pin carried by said bolt; a lower receiver attached to said upperreceiver and having a trigger, and a magazine well proximate to saidtrigger and dimensioned for receiving an ammunition magazine; and a buttstock attached to said lower receiver.
 8. The rifle of claim 7, whereinsaid barrel extension has two holes formed therein and where said barrelis pulled rearward against said receiver when said two screws areinserted and tightened in said two holes.
 9. The rifle of claim 7,wherein said upper receiver has a proximal end and a distal end, andwherein said rifle further comprises a charging handle carried by saiddistal end of said upper receiver.
 10. The rifle of claim 9, whereinsaid charging handle is non-reciprocating.
 11. The rifle of claim 7,wherein said bolt carries an extractor, said extractor being fastened tosaid bolt with a threaded pin.
 12. The rifle of claim 7, wherein saidbolt has a recess and a pair of opposing holes on opposing sides of saidrecess, and wherein said bolt includes an extractor dimensioned to bereceivable in said recess, said extractor having a hole formed therein,and wherein said hole in said extractor and said opposing holes arethreaded, and wherein said bolt includes a threaded pin in said opposingholes and said hole in said extractor.
 13. The rifle as recited in claim7, wherein said upper receiver further comprises a shell ejection portand wherein said rifle further comprises a shell deflector fastened tosaid upper receiver adjacent to said ejection port so that ejectedshells are deflected by said shell deflector.
 14. The rifle as recitedin claim 7, wherein said gas block assembly further comprises aregulator having plural user-selectable positions, a position of saidplural positions providing a different back pressure to said gas blockassembly so that back pressure on said piston may be altered.
 15. Therifle as recited in claim 7, wherein said upper receiver has a proximalend and a distal end, and wherein said upper receiver has a slot formedin said distal end and wherein said rifle further comprises: a chargingsled carried within said receiver on said first rails; a charging handleattached to said charging sled and extending from within said upperreceiver through said slot, said charging handle configured for a userto pull said charging sled between said proximal position and saiddistal position; and a hook pivotally mounted to said charging sled andpivoting between a hooked position and an unhooked position, said hookbeing in said hooked position to pull said upper bolt carrier to saiddistal position after charging said rifle and being in said unhookedposition when said rifle is operating in said firing cycle.
 16. Therifle as recited in claim 15, wherein said upper receiver carries aspring biasing said hook in said unhooked position, when said chargingsled is in said distal position.
 17. The rifle of claim 7, wherein saidbolt further comprises a cam pin and upper receiver has a cam pathformed therein, said cam pin extending through said bolt and into saidcam path, said cam pin following said cam path as said upper boltcarrier and lower bolt carrier move from a distal position to a proximalposition and back to a distal position in a firing cycle, said cam pathconfigured so that said bolt is not unlocked from said chamber untilpressure in said chamber is reduced.
 18. The rifle of claim 7, whereinsaid upper bolt carrier is brazed to said lower bolt carrier.
 19. Therifle of claim 7, wherein said upper bolt carrier has a closed passageformed therein said passage containing a powder freely movable withinsaid passage.
 20. The rifle of claim 7, wherein said piston strikes saidupper bolt carrier in the center of mass of said upper bolt carrier.